1. Field of the Invention
The present invention relates to a switching installation, suitable in particular for voltages of over 1000 V, comprising a circuit breaker, which is connected to a cable connection, and optionally a disconnector for making or breaking a conductive connection between the cable connection and a rail system, and an electrically insulating barrier for shielding an element of the switching installation which is under voltage in operation.
More in particular, this invention relates to a switching installation according to the preamble of claim 1.
2. Background Information
Such a switching installation is known from patent publication CH-A-200 798.
Since most switching installations are of three-phase design, there are also three of each of the abovementioned components per functional unit (also referred to as a field), these components being physically and electrically separated from one another for each phase.
Furthermore, the phases of a switching installation of this type are generally accommodated as a physical entity in a surrounding switchbox, in which, on account of the considerable differences in potential, a certain distance has to be maintained between the various voltage-carrying parts and other electrically conductive parts of the switch cabinet, in order to prevent an electrical sparkover or breakdown between these various parts. As well as the voltage used, this distance is also dependent on the type of circuit breaker used, such as for example air circuit breakers, oil circuit breakers, vacuum circuit breakers, etc. and on the insulation medium used between the various parts of the switching installation, such as for example gas (air, SF6, and the like), liquid (oil), solid (casting resin), etc.
On account of the space taken up and also on account of the higher materials and transport costs, it is aimed to make switching installations as compact as possible, and a combination of circuit breakers and insulating media are used to enable a compact design to be achieved. For example, the combination of vacuum circuit breakers with SF6 insulation is in widespread use in order to obtain a compact switching installation. Although there is a desire to move away from SF6 as insulation medium, on account of the negative consequences for the environment, this gas is nevertheless still in widespread use, since there are insufficient alternatives available in particular with a view to achieving the compact design.
A switching installation which is based on the object of providing a compact design is known, for example, from American Patent Application US-A-2001/0005306, which describes a switching installation with a cable connection and a rail system, between which there is a vacuum circuit breaker by means of which a cable and a rail can be connected to one another. The installation also comprises a drive mechanism and a means for disconnecting cable and rail from one another by means of a disconnector, as well as a grounding feature. The installation disclosed comprises a number of compartments, such as a cable compartment, a rail compartment and a switching compartment. Use is made of insulating walls in the switching installation in order to electrically shield specific components from other specific components.
The known switching installation has the drawback that, on account of the high voltages which are to be used at various parts of the switching installation, a considerable dimension is required if air is to ensure sufficient electrical insulation. A number of insulating walls are also used, but not for all the relevant components of the switching installation. Furthermore, the known switching installation requires considerable work to set it up.
Furthermore U.S. Pat. No. 4,879,441 has disclosed a switching installation in which use is made of a dielectric barrier comprising an insulating plate which is bent in such a manner that three sides which are perpendicular to one another are formed. The plate formed in this way is secured around each vacuum circuit breaker for each phase, in such a manner that the vacuum circuit breakers and a part of the drive rod are surrounded on three sides by said plate, the open sides of the insulating plate being located on the front, top and bottom sides.
The addition of a barrier of this type ensures that the dielectric strength between specific parts is increased, with the result that either a higher voltage or shorter distance between said parts having a different voltage potential can be used.
Although the addition of the known dielectric barrier achieves a significant improvement, further improvement is still possible, in particular with regard to the compactness of the switching installation.
Therefore, it is an object of the present invention to provide a switching installation which has a dielectric shielding which is such that optimum compactness and a simple assembly of components of the switching installation as a whole is made possible without it being necessary to use the insulating medium SF6, despite the known fact that the dielectric strength of SF6 is greater than that of air.